Pressure switch arrangement

ABSTRACT

An arrangement in which a microswitch becomes actuated when a predetermined fluid pressure has been attained. The fluid under pressure is introduced within the tubular spring member having one end which deflects in accordance with the magnitude of the pressure. The deflecting end of this tubular spring member has an abutment member which actuates the switch supported in a bracket pivotably arranged on the housing. A rotatable knob positions angularly the switch bracket, through a cam follower linkage, for varying the pressure at which the switch becomes actuated. The rotatable knob is provided with a scale from which the angular positions of the knob may be read. A lever is also positioned by the knob and a second abutment member on the lever cooperates with the switch bracket so that the distance between this second abutment member and the pivoting axis of the lever may be varied.

United States Patent [72] Inventors Rainer Bartholomsus; I

, v Hans Wolfges, both of Lohr, Germany [21 Appl. No. 884,795 [22] Filed Dec. 15,1969 [45] Patented Aug. 31, 1971 [73] Assignee G. I... Rexroth Lahrer Elsenwerk GmbH Lohr Main, Germany [32] Priority Dec. 14, 1968 [33] Germany [3,1] P18 14754.1

[54] PRESSURE SWITCH ARRANGEMEN 9 Claims, 5 Drawing Figs.

[52] US. Cl zoo/81.3,

' 200/167 R [51] Int. Cl. H0lh 35/36 [50] Field oiSearch 200/166 M, 81.8, 83.34, 83.91, 82.2, 81, 819,166 1-1, 167 R; 337/322, 323

[56] References Cited UNlTED STATES PATENTS 2,082,493 6/1937 Hartman 200/166 H 2,421,267 5/1947 Huber 200/166 1-1 2,853,567 9/1958 Kock 200/166 M 3,095,487 6/1963 Jokela il i I 3,135,843 6/1964 Margerie Primary ExaminerD. X. Sliney Assistant Examiner-R. Skudy Attorney-Michael S. Striker ABSTRACT: An arrangement in which a microswitch becomes actuated when a predetermined fluid pressure has been attained. The fluid under pressure is introduced within the tubular spring member having one end which deflects in accordance with the magnitude of the pressure. The deflecting end of this tubular spring member has an abutment member which actuates the switch supported in a bracket pivotably arranged on the housing. A rotatable knob positions angularly the switch bracket, through a cam follower linkage, for varying the pressure at which the switch becomes actuated. The rotatable knob is provided with a scale from which the angular positions of the knob may be read. A lever is also positioned by the knob and a second abutment member on the lever cooperates with the switch bracket so that the distance between this second abutment member and the pivoting axis of the lever may be varied.

[I ill PATENTEU M11231 m 3.602.664-

SHEET 1 [IF 3 Fig.1

INVENQ: RS:

RAIER BARTIIJLU HANS WULFBES PATENTEU was] 1971 SHEET 3 OF 3 I i m m '1 'IIIIIIIIII PRESSURE SWITCH ARRANGEMENT v BACKGROUND OF THE INVENTION pose of varying the switching point of the microswitch.

In pressure switches of the preceding species, the switching point is set through a rotatable knob provided with a scale, and the knob is mounted upon a threaded shaft or spindle projecting from the housing. In securing the rotatable knob onto the threaded spindle or shaft, care must be taken that the zero switching position of the pressure switch agrees with the zero indication of the scale. In view of manufacturing tolerances, the deflection of tubular spring members or Bourdon tubes deviate when subjected to pressure. As a result, no agreement between the scale indication and the actual switching position of the pressure switch might be realized in conventional pressure switches. The scale graduations or scale subdivisions, serve thereby only as an orienting aid for setting the pressure switch.

Accordingly, it is an object of the present invention to provide a pressure switch in which the actual switching position corresponds to the scale indication.

The object of the present invention is achieved by providing that the abutting member for setting the bracket of the microswitch, is arranged on a lever, and the distance between this abutting member and the rotatable axis of the lever is made variable. The lever is, furthermore, settable or adjustable about its rotatable axis through a setting member which operates in conjunction with a scale. Through the use of a lever with an abutting member which is variably spaced from the rotatable axis of the lever, and by providing that the abutting member is used for the setting of the bracket of the microswitch, the setting or adjustment path of the abutting member is made variable for a predetermined angular position of the lever. If, for example, a predetermined pressure setting is applied to the rotatable knob on the lever, agreement between the knob position and the actual pressure at which switching is to take place, may be realized in a simple manner. This results from the condition that the adjustment path of the adjustment member is extended by the missing amount through increasing its distance to the rotatable axis of the lever.

Since the point of contact between the abutting member and the bracket of the microswitch varies as a function of the rotation of the lever and bracket, one may attempt to compensate the associated setting error through, for example, a camshaped surface on the bracket for the microswitch. Compensation of the errors, in this manner, however, incurs considerable manufacturing or fabrication problems. In order to reduce these setting errors to a minimum in a simple manner, the present invention provides that with flat abutting surface on the bracket of the microswitch, the rotational axis of the bracket and lever as well as the abutting surface of the abutting member lie in a common plane, in the average switching position of the bracket. Through the relatively small maximum displacement of the bracket, the setting errors remain within the setting precision of the. rotational knob, in

the present invention, and are therefore negligible.

For actuating the lever,- the setting element is advantageously in the form of a cam connected to a rotational knob, so that a cam follower arranged on the lever transmits to the lever the functional motionprescribed by the cam. The cam follower is made adjustable, and through this feature, the zero position of the scale may be readily made to agree with the zero switching position of the microswitch.

For the purpose of reducing the setting errors when using the cam as the setting member for the lever, the contact point between the follower rod and the cam surface falls advantageously in the center position thereof together with the tangent to the surface of the cam at the contact point from the rotatable axis of the lever. The setting error of the pressure switch with a cam used as the setting member is, furthermore, maintained small when the setting or adjustment direction of the cam follower is in the center position of the cam and through its rotational axis. In order to achieve a compact construction and simple assembly and disassembly of the pressure switch, an integral structure is formed from the lever with the.

SUMMARY OF THE INVENTION A pressure switch arrangement in which a microswitch becomes closed when a predetermined pressure is being registered through predetermined deflection of a tubular spring member. The microswitch is mounted on a pivotable bracket secured to the housing and is actuated by an abutment member located at the free end of the hollow or tubular spring member. When fluid under pressure is introduced in the interior of the spring member, the free end deflects and moves, thereby, the abutment member. A rotatable knob positions angularly the microswitch bracket, through a cam-follower arrangement for the purpose of varying the pressure at which the switch becomes actuated. A scale is operatively provided with the rotatable member for indicating the angular position of this rotatable member or knob. A lever is pivoted about a predetermined axis and is positioned by the knob in accordance with the scale. A second abutment member on the lever cooperates with the microswitch bracket so that the distance between this second abutment member and the pivoting axis of the lever may be varied.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construc tion and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of the pressure switch of the present invention;

FIG. 2 is a plan view of the interior of the pressure switch when the cover of the switch is removed;

FIG. 3 is a plan view of the housing cover when viewed from below of the pressure switch;

FIG. 4 is an assembly view taken in the direction A in FIG. I with the sidewall partially removed and with cross section in the region of the rotatable knob, in accordance with the present invention; and

FIG. 5 is an assembly viewof another embodiment of FIG. 4 with another housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS as a bourdon tube. An extension member 4a is welded onto I the free end 4 of the tubular spring 2,. and an abutment and a compression spring 16 forces the lever toward a cam 17..

A follower pin 20 within a recess 18 of the lever 14, is in contact with the outer circumference 19 of the cam 17. The follower pin 20 may be adjusted in the direction of the cam 17, through a screw 21. The lever 14 is rotatable or pivotable about the axis 22, and an abutting member 23 is guided within a fork-shaped guide 24 of the lever 14, in the proximity of the pivot axis 22. Through means of spring elements 25, the abutting member 23 is pressed against the guide surface 26 without play.

The cam 17 mounted on a camshaft 30, has its surface 28 facing the housing cover 13, held tightly against the surface 29 of the housing cover, through spring elements 31, shown in FIG. 4. A guide member 33 is secured to the camshaft 30, through a clamping pin 32. The guide member 33 has bores 49 into which pins 50 are admitted and reach into a notch 51 of the lock member 52. with the lock 35 and the rotatable knob 36. These pins, thereby, secured the lock member in the guide member 33, in the axial direction. The guide member 33 has a cutout or recess 37 into which a bolt 34 enters when closing the lock 35. In this manner, the key-shaped joint between the guide member 33 and the lock facilitate the radial positioning of the cam 17 through the rotatable knob into the desired position. A covering disc 38 with a scale 39 is mounted upon the housing cover 13. The bracket 8 abuts the abutting member 23 at the height of the actuator 7 of the microswitch. To secure the bracket 8 to the abutting member 23 against vibration and loose play, a spring 40 is used to act against the bracket 8 in the direction of the abutting member 23.

The pivot axis 22 of the lever 14, the abutting surface 41 of the abutting member 23, shown in FIG. 3, as well as the pivot axis 42 of the bracket 8, shown in FIG. 2, all lie in a common plane in the intermediate switching position of the.

microswitch 9 secured to the bracket 8.

An orifice or throttle 44 is provided at the pressure connection 43 of the tubular spring member 2, for the purpose of applying damping action to the fluid within the spring member 2, for sudden and sharp variations in pressure.

At the outer end of the extension 4a welded onto the end 4 of the tubular spring member, is a bent lug 45 secured in place with a screw 45a. This lug 45 has a portion 46, shown in FIG. 4, for the purpose of limiting the displacement of the tubular spring member, and functions in conjunction with a fixed abutting member 47 at the housing. To avoid stressing the housing 1 through, for example, actuation of an uneven or nonflat surface as on an unfinished front surface of a control installation, the housing is secured to a flexible or elastic housing plate 1a, as shown in FIG. 5. The housing plate 1a forms the securing element for the pressure switch. In this design, the housing cover 13a forms a complete unit with the housing 1 for the purpose of increasing the stability of the pressure switch. The housing plate In forming the base of the housing has, thereby, the sole function of carrying the housing.

The calibration of the pressure switch is carried out in a manner so that the tubular spring is subjected to pressure of approximately one-fourth of the maximum pressure. The rota tional knob 36 is then rotated or displaced until the microswitch 9 becomes actuated and the position of the rotational knob is then read off through means of the scale provided therewithflbe tubular spring is then subjected to a pressure of approximately three-fourths of the maximum pressure, and the rotational knob 36 is again displaced until the microswitch 9 becomes actuated. The new position of the readings from this scale does not agree with the difference in the two pressure positions of the tubular spring, the spacing of the abutting member 23 with respect to the pivot axis 22 of the lever 14, is varied until the scale difference readings agree with the pressure settings. This adjustment in the spacing of the abutting member 23 is accomplished through the setscrew 27. When the scale readings agree with the pressure differences used for calibration purposes as determined through two on or off switching points of the tubular spring, the indicator 48 of the rotatable knob 36 is set to zero on the scale 39.

For this purpose, the rotational knob 36 is rotated to the extent that the indicator 48 coincides with the center of the scale, and the tubular spring is subjected to pressure which corresponds to that indicated by the indicator 48 on the scale. The setscrew 21 with the abutting follower 20 is then adjusted until the microswitch 9 becomes actuated. With the conclusion of this operation, the zero setting and the calibration of the pressure switch has been carried out.

When rotating the rotational knob 36 is the unlocked state, to a predetermined value on the scale, the lever 14 is pivoted or rotated by a predetermined amount about its axis 22, as a result of the follower pin 20 and the cam 17. With this angular rotation of the lever 14, the abutting member 23 joined thereto is also rotatably moved. Since the bracket 8 abuts the member 23, this bracket becomes rotated by a corresponding amount, about its axis 42. The actuator 7 of the microswitch 9 held by the bracket 8, assumes thereby a position whereby the microswitch becomes actuated through corresponding deflection of the member 5 on the tubular spring, which is caused as a result of the pressure applied to this tubular spring 2.

In the detailed construction of the pressure switch of the present invention, the right-angled lever 14 is secured through a screw 15 to the cover 13. The pivot point 22 of the lever 14, shown in FIGS. 2 and 3, passes through the axis of the screw 15. The adjustable follower 20 is arranged at the longer lever arm of the lever 14, and is brought tobear against the cam 17, through a spring 16 which is also mounted in the cover. At the smaller arm of the lever 14, is the adjustable abutment member 23. This abutment member 23 abuts its surface 41, against the bracket 8 of the microswitch 9. The bracket 8 is secured within the housing by the screw '11, and is rotatable about the axis 42. The spring 40 serves to maintain the bracket 8 against the abutting surface 41 of the member 23. The contact point of the convex-shaped abutting surface 41 is denoted by the reference numeral 41b. If, now, the cam 17 is rotated in the clockwise direction, in FIG. 2, through rotation of the knob 36, for example, the lever 14 is rotated about its pivot axis 22, through the follower 20, and in counterclockwise direction. Through the abutting member 23, the bracket 8 is rotated about its axis 42 in clockwise direction. The angular displacement of the bracket 8 is dependent upon the space of the contact point 41b to the pivot axis 42 of the bracket 8 and to the pivot axis 22 of the lever 14, for identical angular rotations of the cam 17. If, through actuation of the adjusting screw 27, shown in FIG. 3, the abutting member 23 is displaced in the direction of the pivot axis 22. in accordance with the arrow 41a in FIG. 2, the spacing between the contact point 41b and the pivot axis 42 becomes diminished. At the same time, the spacing between the contact point 41b and the pivot correspondingly. The spacing between the actuator 7 and the abutting member 5 on the end 40 of the tubular spring, corresponds to a predetermined pressure difference.

If the tubular spring 2 is subjected to pressure, the end 40 of the tubular spring is deflected in the direction of the actuator 7 of the microswitch 9, and this deflection is a predetermined amount corresponding to the applied pressure. When the deflection of the end 4a is of the amount equal to the spacing between the actuator '7 of the microswitch 9 and the abutting member 5, then actuator 7 is contacted and the microswitch is actuated.

The switching point of the microswitch must agree with the indicated value of the scale. In order to obtain such an agreement, the pressure switch must be calibrated. The calibration is accomplished through corresponding setting of the abutting member 23 and the follower pin 20 which are both arranged or mounted on the lever 14. The cam 17 is, in this connection, rotated in the clockwise direction until the indicator 48 points to the maximum value of the scale 39 through rotation of the knob 36. In accordance with the diagram of FIG. 1, this corresponds to a value of 400 kg./cm. This corresponds, at the same time, to the maximum spacing between the actuator 7 and the abutting member 5 of the tubular spring portion 4. The tubular spring is then subjected to a pressure of, for example, 100 kg./cm. with the aid of a manometer. As a result of such applied pressure, the tubular spring end 4 is deflected, and the abutting member is deflected therewith by a determined amount. Through the rotational knob 36, the cam 17 is then rotated back until the microswitch is actuated. Thus, by rotating back the cam 17, the spacing between the actuator 7 and the abutting member 5 is diminished until finally both are in contact and the microswitch 9 becomes, thereby, actuated.

Assume that the microswitch 9 is actuated at 80 atmospheres gauge pressure upon the scale 39. The deviation from the scale is thereby 20 atmospheres. After reading of? these values, the knob is again rotated to 400 atmospheres and the tubular spring is now subjected to a pressure of, for example, 300 atmospheres. The rotational knob is then again rotated back until the microswitch 9 becomes actuated. Assume that at the instant that the switch becomes actuated, the indicator 48 of the rotational knob points to 350 atmospheres on the scale 39. This reading is 50 atmospheres more than the pressure applied to the tubular spring. As a result, the cam 17 must be rotated by an amount of 270 atmospheres, i.e., 80 to 350 atmospheres on the scale, for a pressure increase of 200 atmospheres ranging from 100 to 300 atmospheres. This implies that the deflection of the bracket 8 through the lever 14 and the abutting member 23, is too small at the pressure difference of 200 atmospheres. For the purpose of increasing the deflection of the bracket 8 for a predetermined angular rotation of the cam 17, the abutting member 23 must be moved or displaced in the direction of the pivot axis 42. Thus, the abutting member 23 must be moved with the aid of the setting screw 27, in FIG. 3, in the direction of the follower 20.

In order that the scale difference in the preceding example agrees with the pressure difference, the rotational knob is set to 280 atmospheres, and the abutting member .23 is set through the adjusting screw 27 until the microswitch 9 becomes actuated. The set value on the scale remains to be brought into agreement with the pressure of 300 atmospheres applied to the tubular spring. This is accomplished by rotating the knob from 280 atmospheres to 300 atmospheres on the scale 39. The bracket 8 becomes thereby deflected by a corresponding amount of 20 atmospheres. This amount is then made reversible through setting of the follower in the direction of the double-arrow 20a in FIG. 2, with the aid of the setscrew 21, to the extent that the microswitch becomes actuated. Whereas the deflection of the bracket 8 per unit of angular rotation of the rotational knob, and thereby the deflection of the tubular spring, is made dependent upon the applied pressure through the setting screw 27, the setscrew 21 is used for obtaining agreement between the scale indication and the applied pressure to the tubular spring. This last-mentioned means can be replaced by a rotatable scale which, however, is inherently more complex in construction.

In a further feature of the present invention, the rotatable knob 36 is rotated to the extent that the indicator 48 points to 200 atmospheres on the scale 39. This situation corresponds to an intermediate deflection of the bracket 8. In this configuration, the pivot axis 42 of the bracket 8, the pivot axis 22 of the lever 14, and the contact point 41b between the bracket 8 and the abutting surface 41 of the member 23, lie in a common plane which may be evident from FIG. 2. Thus, this common plane corresponds to the abutting surface of the bracket 8'in FIG. 2. r

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of pressure switches differing from the types described above.

While the invention has been illustrated and described as embodied in pressure switches, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A pressure switch arrangement comprising, in combination, a housing; a tubular spring member; means for'admitting a medium under pressure into the interior of said tubular spring member through one end thereof for deflecting said member as a function of the magnitude ofsaid pressure; a first abutment member at the other end of said spring member so as to move in correspondence with the deflection of the latter; switch means actuated by said first abutment member; switch supporting means pivotally secured to said housing for supporting said switch means; and means for adjusting the angular position of said switch supporting means for varying the pressure magnitude at which said first abutment member actuates said switch means, said adjusting means comprising lever means pivotable about a predetermined axis, a second abutment member on said lever means and engaging said switch supporting means, means for varying the distance between said second abutment member and said predetermined axis, a rotatable adjustable member operatively connected to said lever means for pivoting the same about said predetermined axis, and scale means cooperating with said rotatable member for indicating the angular position thereof and thereby the magnitude of pressure at which said switch means will be actuated.

2. The pressure switch arrangement as defined in claim 1, wherein said switch supporting means has a substantially flat abutting surface against which said second abutment member abuts, wherein said switch supporting means is pivotable to opposite sides of an intermediate position, and wherein the pivot axes of said switch supporting means and said abutting surface lie substantially in a common plane when said switch supporting means is in said intermediate position.

3. The pressure switch arrangement as defined in claim 1, and including cam means coupled to said rotatable member; and cam follower means in contact with said cam means and carried by said lever means to change the angular position of the latter in correspondence with the position of said cam means.

4. The pressure switch arrangement as defined in claim 5, wherein said cam means is adjustable between a pair of end positions, wherein said cam follower means is carried by said lever means adjustable in a predetermined direction, and wherein the direction of adjustment of said follower means passes through the axis of said cam means when the latter is in an intermediate position between said end positions.

5. The pressure switch arrangement as defined in claim 3, wherein the contact point between said cam follower means and said cam means coincides with the point of tangency of a tangent to the functional surface of said cam means from the 8 secured to said housing, sadh ousing being an integral structure with said housing cover means, the face of said housing being formed by said elastic housing plate means.

9. The pressure switch arrangement as defined inclaim 3, wherein said cam means comprises a disc cam with functional surface on the rim of said cam, said cam follower means comprising a rod-shaped member in substantially point contact with said rim surface of said cam and being displaced in accordance with the functional surface ofsaid cam. 

1. A pressure switch arrangement comprising, in combination, a housing; a tubular spring member; means for admitting a medium under pressure into the interior of said tubular spring member through one end thereof for deflecting said member as a function of the magnitude of said pressure; a first abutment member at the other end of said spring member so as to move in correspondence with the deflection of the latter; switch means actuated by said first abutment member; switch supporting means pivotally secured to said housing for supporting said switch means; and means for adjusting the angular position of said switch supporting means for varying the pressure magnitude at which said first abutment member actuates said switch means, said adjusting means comprising lever means pivotable about a predetermined axis, a second abutment member on said lever means and engaging said switch supporting means, means for varying the distance between said second abutment member and said predetermined axis, a rotatable adjustable member operatively connected to said lever means for pivoting the same about said predetermined axis, and scale means cooperating with said rotatable member for indicating the angular position thereof and thereby the magnitude of pressure at which said switch means will be actuated.
 2. The pressure switch arrangement as defined in claim 1, wherein said switch supporting means has a substantially flat abutting surface against which said second abutment member abuts, wherein said switch supporting means is pivotable to opposite sides of an intermediate position, and wherein the pivot axes of said switch supporting means and said abutting surface lie substantially in a common plane when said switch supporting means is in said intermediate position.
 3. The pressure switch arrangement as defined in claim 1, and including cam means coupled to said rotatable member; and cam follower means in contact with said cam means and carried by said lever means to change the angular position of the latter in correspondence with the position of said cam means.
 4. The pressure switch arrangement as defined in claim 5, wherein said cam means is adjustable between a pair of end positions, wherein said cam follower means is carried by said lever means adjustable in a predetermined direction, and wherein the direction of adjustment of said follower means passes through the axis of said cam means when the latter is in an intermediate position between said end positions.
 5. The pressure switch arrangement as defined in claim 3, wherein the contact point between said cam follower means and said cam means coincides with the point of tangency of a tangent to the functional surface of said cam means from the pivoting axis of said lever means, when said cam means is in an intermediate position.
 6. The pressure switch arrangement as defined in claim 3, including a housing cover for said housing, said lever means with said cam means and said rotatable member forming one unit with said housing cover means.
 7. The pressure switch arrangement as defined in claim 1, including elastic housing plate means, said housing being flexibly secured to said housing plate means.
 8. The pressure switch arrangement as defined in claim 6, including housing plate means elastically arranged and secured to said housing, said housing being an integral structure with said housing cover means, the face of said housing being formed by said elastic housing plate means.
 9. The pressure switch arrangement as defined in claim 3, wherein said cam means comprises a disc cam with functional surface on the rim of said cam, said cam follower means comprising a rod-shaped member in substantially point contact with said rim surface of sAid cam and being displaced in accordance with the functional surface of said cam. 